Generally, bicycle derailleurs are so constructed that the holder for the outer sheath is supported mainly to the base member, the fixture for the control wire is provided at one linkage member or the movable member, and the control wire drawn out of the holder is secured to the fixture. In this configuration the control wire is operated to transform the linkage mechanism so as to move the chain guide in reciprocation axially of the multistage sprocket assembly.
In this case, the control wire moves within the holder and the portion thereof which is drawn out of the holder and secured to the fixture swings laterally following the reciprocation of the chain guide.
Hence, the wire will come into contact with the edge at the exit of the holder to increase its contact resistance, thereby creating the problem in that the speed change efficiency is diminished.
The inventor has hitherto proposed a derailleur as disclosed in Japanese Utility Model Laid-Open Gazetta No. Sho 57-194,886, in which the holder is provided at its exit for the wire with a guide which is formed of a slippery material having a smaller coefficient of friction and which has a guide bore so that the control wire is guided through the guide between the exit of the holder and the fixture, thereby reducing the contact resistance of the wire with respect to the holder.
The guide, which has been formed mainly of synthetic resin, has a problem with wear resistance. Also, the guide, which is fixed to the holder, varies in its position when the holder is adjusted to change its position. As a result, the length of the wire drawn out from the exit at the holder and secured to the fixture also varies. In particular, in a case where a positioning mechanism for the chain guide is provided at the operating lever side, even when the operating lever is operated in a proper range, the amount of movement of the chain guide is not constant. Hence, conjointly with a change in a relative effective length of the wire to the outer sheath caused by wearing of the guide, the speed change efficiency is deteriorated to that extent.